This invention relates to grinding mill. More particularly, this invention relates to a lining for a grinding mill. The present invention also relates to an associated method for manufacturing a grinding mill lining.
A grinding mill generally comprises a cylindrical drum which is mounted for rotation about its longitudinal axis. A grinding medium such as pebbles, steel balls, or ceramic balls is fed to the drum, together with the material to be pulverized. During rotation of the drum about its longitudinal axis, the grinding medium and the material to be ground are carried up the side of the drum, to subsequently fall to the bottom of the drum. The grinding occurs principally by attrition and impact within the grinding mill charge.
In order to protect the drum from the grinding action and to thereby lengthen the life of the grinding mill, the drum is provided with a metal or a rubber lining. A lining for the cylindrical inner surface of a grinding mill drum is either an assembly of modular lining sections or an assembly of elongate wedge-shaped ribs forcibly held in place with circumferentially extending spacers. The longitudinally extending ribs and/or supplementary lifter bars facilitate the carrying of the grinding medium and subject material with the drum during rotation thereof, thereby creating the grinding action.
Rubber linings are especially advantageous owing to their relatively light weight. Rubber linings are safer and faster to exchange. In addition, rubber linings result in less load on the bearings and less stress on the mill heads. Other advantages of rubber linings are a reduced noise level and reduced operating costs.
Until now, rubber linings have been used exclusively in slow or regular speed grinding mills, with angular velocities up to approximately 80% of the critical speed (the rotational speed at which the drum contents adhere to the liner by virtue of centrifugal forces). In addition, rubber linings have not been economical with large diameter grinding balls. Accordingly, only metal linings have been used at high rotational speeds and/or with large diameter grinding media.
The ribs and spacers of conventional grinding mill linings generally form recesses along the inner surface of the grinding mill. In using such a conventional grinding mill to pulverize gold ore, gold particles are frequently trapped in the recesses in the mill lining. This trapping of the gold material, known as "gold hold" can result in substantial loss of gold material or increased costs in retrieving the gold material from the lining. The same is true for other precious metals.